The present invention relates to a semiconductor device composed using a material of a high permittivity, and more particularly to the semiconductor device provided with a gate structure composed using the material of a high permittivity.
As the semiconductor device is made finer, the gate length of the transistor becomes as short as 0.15 μm. Hence, the thickness of a gate insulating film is requested to be as thin as 2 nm or less in the case of composing the gate insulating film using SiO2. Such a thin insulating film as that causes a non-negligible amount of current to be tunneled through the insulating film itself. It has been thus considered that the physical thickness of the insulating film is made thicker as keeping the high permittivity characteristic by using an insulating material of a higher permittivity than SiO2.
As candidates for the material of a high permittivity, aluminum oxide, zirconium oxide, hafnium oxide, and so forth may be referred. (For example, see the Lecture No. 3.3 (pages 56 to 60) of the Extended Abstracts of International Workshop on Gate Insulator 2001.)